This invention relates to automatic pool cleaners of the type adapted to be connected to a flexible hose, which is connected to the inlet of a pump circulating water through the pool. One such cleaner is marketed throughout Australia and other countries under the trade mark xe2x80x9cZoltans Automatic Pool Cleanerxe2x80x9d. Another version is sold under the trademark xe2x80x9cKreepy Kraulyxe2x80x9d. One version of the Kreepy Krauly cleaner is described in the expired Australian Patent Specification No. 505209.
Such automatic pool cleaners can comprise a body having an inlet, a flexible seal mounted on the body to bear against a surface of a wall or floor of a pool, a flip-flop valve capable of moving back and forth between two extreme positions for controlling water flowing through a body and in doing so produce a water hammer effect which acts on the automatic cleaner to propel it across the surface. An elongated member connects the body to the inlet end of a flexible hose. The elongated member has two passages formed by two parallel tubes through which the water flows alternately.
It has been found that the flip-flop valve performance is substantially and unexpectedly affected by small changes in structure and thereby substantially affects the efficiently of the automatic pool cleaner. It has been found that the efficiency of the automatic pool cleaner can be substantially improved if the hammer valve member forming the critical part of the flip-flop valve is altered.
It is therefore an object of the invention to devise an improved automatic pool cleaner, which may be effective with a less powerful suction means than is presently possible.
It is also an object of the invention to provide an improved automatic pool cleaner which overcomes or ameliorates one or more disadvantages of known automatic pool cleaners.
Thus, according to the present invention, there is provided an automatic pool cleaner of the type having an elongated body with an inlet, a flexible seal mounted on an end of the elongated body to bear against the surface of the wall or floor of the pool, a flip-flop valve positioned adjacent to the inlet of the elongated body and capable of moving back and forth between two extreme positions for controlling the flow of water through the elongated body and in so doing producing a xe2x80x9cwater hammer effectxe2x80x9d which acts on the automatic pool cleaner to propel it across the surface and wherein the flip-flop valve includes a substantially wedge-shaped hammer valve member formed by two spaced, substantially triangular sides interconnected by a central body narrower than the sides and an end surface connecting respective ends of the substantially triangular sides such that the hammer valve member has continuous sides and cavities between the sides due to a central body being narrower than the triangular sides, the end surface having indentations to be engaged by flow of water around the hammer valve member and into the inlet of the elongated body to aid the flip-flop action.
The indentations can be of the order of 20 to 30% of the end surface allowing ready flow around the hammer valve member while providing sufficient reaction of the water flow to aid the flip-flop action. Preferably the end surface is curved with the radius of curvature at least equal to the length of the wedge-shaped hammer.
In one form, the indentations can be spaced, circular indentations extending in two lines on either side of a longitudinal center of the end surface. The indentations can be substantially hemispherical such that their depth is of the order of about their radius.
The substantially wedge-shaped hammer valve member can be less than 80 grams and preferably less than 75 grains.
Using a light hammer valve member provides a faster flip-flop action and thereby a greater suction seal. Further, the lighter the hammer valve member the smoother the flip-flop action as there is less vibration which results in less lateral knocking motion that could break the suction seal of the automatic pool cleaner from the pool. This is particularly advantageous in cleaning higher up the walls of the pool. The spaced, circular indentations provide unexpectedly substantial initiation improvement and increased suction seal through providing flow friction points and/or turbulence effect and provide continuing aid in the flip-flop action of the hammer valve member. It avoids the known problem of earlier cleaners using heavier flip-flop valves, such as greater than 90 grams, to make use of the weight to initiate the flip-flop action when suction has begun. Such systems were particularly ineffective in cleaning walls of pools and often had the suction seal broken by a violent xe2x80x9cwater hammer effectxe2x80x9d. Further such systems require a large pool vacuum system to cope with the weight and to compensate for the suction seal breakages.